The present invention relates to a dual magnetic head for reading and writing information from and to a magnetic recording medium in a high track density mode and a low track density mode.
A conventional magnetic head is disclosed in Japanese Patent Laid-Open No. 28913/1987. The head has a high TPI (Track Per Inch) core and a low TPI core having a high TPI read/write (R/W) gap and a low TPI R/W gap, respectively. The two cores are attached with each other and arranged in the radial direction of a floppy disk. The high TPI gap has a gap width smaller than that of the low TPI gap. A pair of erase gaps provided on an erase core are located at opposite sides of the low TPI gap in order to form guard bands on a floppy disk at opposite sides of a low TPI track.
The drawback with the conventional dual magnetic head is as follows. Assume that the high TPI core is used to read signals from a target track, i.e., a high TPI track recorded at high TPI. Since the erase core assigned to low TPI recording slides on tracks other than the target track, the erase gaps sense the magnetizations of those tracks to generate unnecessary magnetic flux in the erase core. The unnecessary magnetic flux leaks to the high TPI core and thereby deforms the waveform of magnetic flux which is developed in the high TPI core and representative of the magnetization of the target track. As a result, noise is introduced into the output signal of the high TPI core.